Apparatus for calcining phosphate rock



W1. SHOELD.

APPARATUS FOR CALCINING PHOSPHATE ROCK.

APPLICATION FILED FEB. 24-. 1920.

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UNITED STATES PATENT OFFICE.

MARK SHOELD, or CHICAGO, ILLINOIS, AssIGNoR T0 ARMOUR FERTILIZER wo-Rxs, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW JERSEY.

APPARATUS FOR CALCINING PHOSPHATE ROCK.

Application filed February 24, 1920.

To all whom it may concern:

Be it known that I, MARK SIIoELD, a subject of the King of Sweden, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Apparatus for (Jalcining Phosphate Rocks, of which the following is a specification.

t has been proposed, heretofore, to calcine round natural phosphate-rock to render the phosphate available in ammoniumcitrate soluble form by gradually heating to the re uired temperature a mixture of such finelyivided rock and sodium acid sulfate, or other suitable salt, in a furnace of proper construction, such as an inclined, internally fired, rotary kiln. I have discovered, however, that if the ground mixture to be treated is gradually or relatively-slowly heated to the required reaction temperature, as has heretofore comprised the suggested procedure, as by introducing the mixture at the upper end of a comparatively-long, inclinedkiln, and permitting it to progressively travel downthe kiln, a preliminary,

undesired or detrimental lumping up or sin-- tering of the material takes place, which lowers in substantial degree the percentage of the material converted into available form at the higher temperature of the conversion reaction.

-material is subject to two sintering actions,

to the reaction temperature, the objectionable detrimental results of the f rst sintering are in large measure, if not entirely, overcome, or, stated somewhat otherwise, the

heating of the material is so quick and rapid that the lower critical sintering temperature is passed without the injurious or wasteful sintering occuring to any objectionable degree. In carrying out this processin its preferred form, a slurry stream of the material to be treated is played by means of a suitable nozzle in a smooth and unbroken stream Specification of Letters Patent.

Apparently, the treated Patented Oct. 18, 1921.

Serial No. 360,959.

invention being the provision of a simple,

inexpensive, but efficient appliance 'by which this process may be practised commercially and economically. v

In order that those skilled in this art may have a full and complete understanding of an apparatus incorporating the features of this invention, in the accompanying drawings, I have illustrated a preferred and desirable embodiment of the same in more or less diagrammatic form.

In these drawings, in which like reference characters refer to the same parts' in the two views,

Figure 1 is a central, vertical section through the rotary inclined kiln; and

Fig. 2 is a horizontal section above the kiln. By reference to the drawings, it will be understood that the apparatus comprises an ordinary, but rather short,-inclined, internally-fired, rotary kiln 10 supported on rollers 11, 11 mounted on suitable pillars 12,12 and revolved in the usual way by a gear 13 driven by a pinion 14: on the top of a central pillar 15 and revolved by any suitable source of power, not shown. Convenient dimensions for sucha rotary cylinder or kiln are 7 feet in diameter and sixteen feet in length with a substantial pitch, as shown, for the relatively-quick delivery or discharge of the material.

The Open-ends of the kiln-are in direct collecting or settling chambers, the upper end of the compartment 16 being connected to the top portion of a checker-work or fiue construction 24 which in turn is connected at its lower end to the corresponding portion 7 of the next checker-work or flue section 25, and this in turn is connected at its upper end to the top .of athird checker-work or fiue structure 26, the latter by means of a flue .or passage 27 being operatively associated with a reversing-valve 28 connected to a stack 29. By means of like checker-work or multiple -flue structures 30, 31, and 32 and a flue 33,

the other or companion chamber 17 is connected to the valve.

This general structure is an ordinary re.

generator system which does not require detaileddescription' or illustration and is usedin the customary way in conjunction. with the usual motor-driven blower and exhauster, not shown, to heat the air passing through the kiln to conserve heat.

The inclined kiln at each end is supplied with a burner, 34 and 35 respectively, ex-

tended through the outer wall of the corresponding chamber or compartment 16 or 17,

. first burneris shut oft, the second one set in operation, and the "-rgenerator valve manipulated to reverse the air and combustion gas flow. Such alternating use of the urners is continued and may be effected manuallyor automatically.

The more important part of the appliance comprises a water-jacketed nozzle 36 extended into the chamber 17 through its outer wall and in line with the lower end of "the kiln, such nozzle being hinged or pivoted at 37 in any approved fashion, whereby the stream delivered therefrom into the kilnmay be caused to take different positions in the .heat zone thereof, that is to say, the stream may be shifted or changed throughout the length of the heat or reaction zone by modifying the position of the nozzle.

The slurry of a consistency, for example,'-.o f

from 45 to 55 degrees Baum, and contain ing ground natural phosphate-rock and sodium acid sulfate, in the approximate proportions of 100 parts'by weight of the former to about 20 to 30 parts of the latter, is fed to the nozzle under pressure loy any suitable means, as by air-pressure, and from the nozzle it is projected directly and quickly into the central heat zone or reaction part of the kiln in a smooth, substantially solid,

the products of combustion passing.

unbroken or undivided stream. This quick and sudden introduction of the material to be calcined into the heat zone of the kiln maintained at a temperature of approximately 1100 degrees to 1400 degrees centigrade, causes a very abrupt and sudden change of temperature of the material so that there is practically no lumping up or I sintering of it until it reaches the reaction temperature, when the phosphate is quickly converted into ammonium-citrate soluble form.

The water of the stream, possibly by its quick conversion or expansion into steam, prevents in large measure, if not entirely, thelumping up or sintering ofthe material undergoing treatment at the lower critical or crucial sintering temperature, andwthe presence of the steam'at the higher reaction temperature facilitates and chemical transformation.

The nozzle is so shaped andformed that the slurry stream delivered therefrom is in I aids in the practically solid condition, thus preventing any spraying or subdivisionof the stream which 'might carry some of the material into those parts of the furnace where it would not be heated "with therequired rapidit to assure a maximum percentage of l availab ephosph'ate.

.By moving orrocking the. position of the nozzle, the streammay be caused to play into "differentportions of the central heat zone, thus' employing the'apparatus to maxi mum advantage and securing the best and most economical effects with the heat developed, at'the same time avoiding any undue cooling action-in any particular part of thekiln. I

In about 10 to 15minutes after. its introduction in slurry form into the furnace, any particularportion of the material treated is delivered or discharged from the lower end of the kiln and is desirably ground for use.

In this application I have illustrated and described an inclined, internally-fired rotary kiln, but the particular style and form of furnacevis more or less immaterial and the type shownis b way of example only and may be modifie to a considerable extent or degree and still be employed satisfactorily for the performance 'of the specified process.

It has also been indicated that the. material to be treated is introduced inthe form of a slurry stream, but in some cases it may possibly be injected into the-heat chamber in dry form, but the losses due'to the finely-divided material being carried along by the ggseous or air. current might be objectiona le.'

One of the vital and essential features of the invention is an apparatus by which the material to be treated may be heated almost instantaneously,such asbysuddenly introducing it into the heat zone, so that its tempera- 1,393,8&0

ture will be very rapidly increased and the critical temperature quickly passed to prevent wholly or in part any detrimental action such as sintering or coalescing of the particles before the reaction temperature is attained.

It will be appreciated, therefore, that the invention is not limited and restricted to the precise and exact structural features shown tion with a regenerator system, those skilled in this art will understand that a kiln could be employed with a burner at one end only and without any regeneration.

I claim':

1. In a calcining structure of the character described, the combination of a furnace, and means to introduce a slurry stream of the material to be treated under pressure directly into the reaction heat zone of such furnace sufficiently suddenly to prevent any substantial detrimental preliminary heat action on the material, substantially as described.

2. In a calcining structure of the char? acter described, the combination of a furnace, and means to introduce a slurry stream of the material to be treated directly into the reaction heat zone of such furnace sufliciently suddenly to prevent any substantial detrimental preliminary heat action on the material, and means to vary the position of such stream, substantially as described.

3.In a calcining structure of the character described, the combination of a rotary inclined-kiln, and means tointroduce the material to be treated in the kiln through its lower end, substantially as described. 4. In a calcining structure of the character described, the combination of an internally-fired rotary inclined kiln, and means to introduce the material to be treated in the kiln through its lower end, substantially as described.

5. In a calcining structure of the character described, the combination of an internally-fired rotary inclined kiln, and means to project the material to be treated in the kiln rapidly through its lower end, substan-v tially as described.

6. In a calcining structure of the character described, ,the combination of an internally-fired rotary inclined kiln, means to project the material to be treated in the kiln rapidly through its lower end, and means permitting variation of the position of said projecting means, substantially as described.

7. In a calcining structure of the character described, the combination of an internally-fired rotary inclined kiln, and a nozzle directed into and adapted to deliver the material to be treated directly into the a reaction, heat zone of the kiln, substantially as described.

8. In a calcining structure of-the char acter described, the combination of an internally-fired rotary inclined kiln, and a nozzle extended through the lower end of the kiln and directed to deliver the material to be treated directly into the, reaction heat zone of the kiln, substantially as described.

9. In a calcining structure of the character described, the combination of an internally-fired rotary inclined kiln, and a movable nozzle constructed and positioned to deliver a relatively-smooth, comparativelyundivided slurry stream directly into the reaction heat zone of the kiln, substantially asdescribed.

10. In a calcining structure of the character described, the combination of an internally-fired rotary inclined kiln, and a movable nozzle constructed to project a relativelysmooth, comparatively-undivided slurry stream of the material to be treated through the lower end of the kiln directly into' the reaction heat zone thereof, substantially-as described.

MARK SHO'ELD. 

